Any professional employee certified by the State Board of Education and employed by a local or regional board of education who leaves such employment for the purpose of entering the armed forces of the United States, as defined in section 27-103, shall be reemployed by the board of education as hereinafter provided, provided such employee makes application for return to such employment within ninety days after receiving a certificate of honorable separation from the armed forces. The board of education shall employ such applicant in his or her former position and duties if such employment is available; and if not, shall employ such applicant in an equivalent position, if available; and if not, shall offer such applicant employment in any available position for which such applicant is qualified. Any employee returning to the employ of the board of education as herein provided shall be credited with the period of such service in said armed forces to the same extent as though it had been a part of the term of employment by such board of education. This section shall not apply to any such employee who, because of voluntary reenlistment, has been absent from the employ of such board of education for a period of more than three years in addition to war service as defined in said section 27-103 or compulsory service and the ninety-day period as hereinbefore provided.